AO Silver Member
Join Date: Mar 2003
Location: United Kingdom
The bearings fail. It's a gearbox design fault because the oil can't reach all the parts properly. Plus a diesel tends to have more torque, meaning more strain on the box.
Mine had a whir for quite a while. When it got worse, I bit the bullet. Fortunately my father-in-law is a brilliant mechanic. We lowered the sub-frame and removed the end casing of the box. All six mainshaft bearings had wear. There wasn't really any large lumps of swarf in the oil but the magnet definitely had traces of metal on it. Looks like it had been doing it's job properly!
You can buy Timken bearing kits off Ebay which will save you a tidy few quid. Once all the shafts were stripped down, cleaned and the bearings replaced along with the races that fit in the gearbox casing, we gave the inside of the gearbox case and bell housing a thorough clean. Once put together, we refilled with 3-litres (yes, the whole 3-litres) of Fuchs Titan Sintofluid gearbox oil (as recommended by Autolusso). It has been perfectly fine and silent for 15,000 miles. I would recommend regular oil changes with the same amount/same brand of oil. With the higher quantity, it should help reach the more tricky areas inside the box. The gearbox has a breather for any unwanted excess but mine never lost any.
It need not be an ridiculously expensive job if you source all the parts carefully and use someone you know or a friendly independent. Alfa specialists may well advise on a replacement box but you could be back to square one in a few thousand miles. If you overhaul and replace your own box, you know what's been done.
It may be an idea to replace the clutch and flywheel at the same time but this would mean complete removal of the subframe. A much bigger job with more expense but, if your clutch bite point is still good, it doesn't slip and still is relatively light, then no point in changing it. If you do, replace the clutch slave inside the bell housing, as these are known to fail too.
Good luck. Try not to get bogged down in the doom of it all. See it as a challenge! I reckon you can sort it for less than £500 if you're careful. Mine only cost me £200 in parts but I was very lucky and the car is fully sorted now!
Rockin' all over the road!